Passengers move through a main security checkpoint at the Denver International Airport. / John Moore, Getty Images

by Bart Jansen, USA TODAY

by Bart Jansen, USA TODAY

WASHINGTON -- The Supreme Court on Monday unanimously overturned a defamation judgment against Air Wisconsin Airlines for reporting one of its pilots as a security risk, which reassured airlines to pass along their suspicions to the Transportation Security Administration.

The pilot, William Hoeper, won a $1.4 million case that the Colorado Supreme Court upheld after airline supervisors reported to TSA that he was "mentally unstable" and could be armed as a passenger on a flight after he failed a simulator test.

But a six-vote majority of the Supreme Court ruled that the law that created the TSA granted immunity "to encourage air carriers and their employees, often in fast-moving situations and with little time to fine-tune their diction, to provide the TSA immediately with information about potential threats."

"No reasonable TSA officer would care whether an angry, potentially armed airline employee had just been fired or merely knew he was about to meet that fate," Justice Sonia Sotomayor wrote in the 18-page decision.

Although all nine justices agreed with that result, Justices Antonin Scalia, Clarence Thomas and Elena Kagan partially dissented in the case, saying that judging whether the complaints against a passenger were "material" and "false" should be left to a jury and not the high court.

"In short, a jury could find that Hoeper did nothing more than engage in a brief, run-of-the-mill, and arguably justified display of anger that included raising his voice and swearing, but that did not cause anyone, including the person on the receiving end of the outburst, to view him as either irrational or a potential source of violence," Scalia wrote in his six-page dissent.

But Scalia said even if the facts were evaluated "in the light most favorable to Hoeper, a reasonable jury would have to find that the report of mental instability would have no effect upon the course of action determined by the TSA."

The Regional Airline Association welcomed the decision that "strongly affirmed that airlines and their employees must report security threats without fear of potential legal ramifications."

Joshua Yount, a partner at Mayer Brown's Chicago office with a Supreme Court practice, said the case confirmed that airlines don't lose their immunity from civil lawsuits when reports about suspicious behavior are imprecise.

"If there was no immunity for such statements, the airlines and their employees would hesitate to provide the TSA with the information it needs to assess threats to flight safety," Yount said.

The incident that sparked the case occurred in December 2004, when Hoeper boarded a plane as a passenger at Washington Dulles International Airport. Hoeper knew he would be fired after failing a series of tests for an unfamiliar plane. He was certified to carry a firearm in the cockpit, although airline officials didn't know if he had a gun with him.

His flight was surrounded on the ground by emergency vehicles and a snow plow before he was removed by law-enforcement officials and detained. But he was released after investigators sorted out what happened, and he caught another flight that day.

Jonathan Cohn, a lawyer representing Air Wisconsin, said pilots, flight attendants and baggage handlers should be forgiven for using imprecise language in reporting possible security threats. He argued that statements about security threats are made urgently, without consulting a script.

Eric Feigin, assistant solicitor general for the Justice Department, said airline workers are instructed to report suspected threats, which TSA officials evaluate. He said misconceptions and exaggerations can occur because airline workers aren't worried about someone's reputation when reporting a threat.

But Kevin Russell, a lawyer representing Hoeper, said calling the 20-year commercial pilot "mentally unstable" was unjustified and sparked the overreaction.